/**
 * Fetch WebRTC failure reason (e.g. wrong host). Pure: same inputs → same output.
 * @returns {Promise<{ wrongHost: { serverHostname: string, clientHostname: string } | null }>} Failure reason or null.
 */
export async function getWebRTCFailureReason() {
  try {
    const res = await $fetch('/api/live/debug-request-host', { credentials: 'include' })
    const clientHostname = typeof window !== 'undefined' ? window.location.hostname : ''
    const serverHostname = res?.hostname ?? ''
    if (serverHostname && clientHostname && serverHostname !== clientHostname) {
      return { wrongHost: { serverHostname, clientHostname } }
    }
  }
  catch {
    // ignore
  }
  return { wrongHost: null }
}